DNA evidence linking Indian tribes to Australian Aboriginal people supports the theory humans arrived in Australia from Africa via a southern coastal route through India, say researchers.
The research, lead by Dr Raghavendra Rao from the Anthropological Survey of India, is published in the current edition of BMC Evolutionary Biology.
One theory is that modern humans arrived in Australia via an inland route through central Asia but Rao says most scientists believe modern humans arrived via the coast of South Asia.
But he says there has never been any evidence to confirm a stop-off in India until now.
Rao and colleagues sequenced the mitochondrial genomes of 966 people from traditional tribes in India.
They report that several of the Indians studied had two regions of their mitochondrial DNA that were identical to those found in modern day Australian Aboriginal people.
The team compared Indian sequences with those from Aboriginal Australians collected in past studies.
Rao and colleagues used computer programs to predict that a common ancestor existed, between the Indian population and Aboriginal Australians, up to 50,000 years ago.
Skeletal remains, dating back between 40-60,000 years from Lake Mungo in New South Wales, also support the theory that modern human arrived in Australia at least as far back as this, he says.
Link through mothers
Rao says he and colleagues sequenced mitochondrial DNA because it is the best type of DNA to use for ancestral studies.
Mitochondrial DNA is passed on by mothers only and does not change much over time.
Evolutionary biologist Dr Jeremy Austin, of the University of Adelaide, says the new data "definitely supports the coastal route hypothesis".
He says that before this research was published, genetic markers from Aboriginal Australians were known to be closely related to markers from traditional Indian and South East Asian peoples.
"But this is the first time people have been able to find these exact same mitochondrial DNA types inside and outside Australia," says Austin.
He says now that a mitochondrial DNA link has been found between tribal Indian populations and Aboriginal Australians it would be interesting to see if a connection exists through the Y chromosome, where DNA is passed only from fathers to sons.